Method for mapping wafers in a wafer carrier

ABSTRACT

The present disclosure relates to a method. The method includes generating a first beam of radiation toward a first slot of a workpiece carrier. The first beam of radiation has a first beam area that is greater than or equal to an area of an opening of the first slot. The method further includes measuring a reflected portion of the first beam of radiation that is reflected toward, and impinges on, a radiation sensor. The method further includes determining if the first slot of the workpiece carrier is holding a workpiece based on the measured reflected portion of the first beam of radiation.

BACKGROUND

Semiconductor device fabrication is a process used to create integratedcircuits that are present in everyday electronic devices. A fabricationprocess is a multiple-step sequence comprising deposition,photolithographic, and chemical processing steps during which electroniccircuits are gradually created on a wafer. During a fabrication processof a multi-dimensional integrated chip (e.g., a 3DIC), a wafer may bemoved to different locations throughout fabrication machinery.

BRIEF DESCRIPTION OF THE DRAWINGS

Aspects of the present disclosure are best understood from the followingdetailed description when read with the accompanying figures. It isnoted that, in accordance with the standard practice in the industry,various features are not drawn to scale. In fact, the dimensions of thevarious features may be arbitrarily increased or reduced for clarity ofdiscussion.

FIG. 1 illustrates a cross-sectional view of some embodiments of aprocess tool comprising an area image sensor for mapping wafers in aFOUP.

FIG. 2 illustrates a three-dimensional view of some embodiments of aprocess tool comprising an area image sensor for mapping wafers in aFOUP.

FIG. 3 illustrates a top view of some embodiments of a process toolcomprising an area image sensor arranged on a transfer robot within asemiconductor fabrication machine housing.

FIGS. 4 and 5 illustrate three-dimensional views of some embodiments ofa method for scanning a first slot of a FOUP to determine if a wafer isin the first slot.

FIG. 6 illustrates a flow diagram of some embodiments of a method fordetermining if a wafer is in a slot of a wafer carrier.

FIGS. 7-9 illustrate cross-sectional views of some embodiments of amethod for mapping wafers in a FOUP.

FIG. 10 illustrates a cross-sectional view of some alternativeembodiments of a method for mapping wafers in a FOUP.

FIG. 11A illustrates a flow diagram of some embodiments of a method formapping wafers in a wafer carrier.

FIG. 11B illustrates a flow diagram of some alternative embodiments of amethod for mapping wafers in a wafer carrier.

FIGS. 12-19 illustrate views of some embodiments of a method for mappingwafers in a FOUP, adjusting the wafers in the FOUP, and remapping theFOUP.

FIG. 20 illustrates a flow diagram of some embodiments of a method formapping wafers in a wafer carrier, adjusting the wafers in the wafercarrier, and remapping the wafer carrier.

DETAILED DESCRIPTION

The following disclosure provides many different embodiments, orexamples, for implementing different features of the provided subjectmatter. Specific examples of components and arrangements are describedbelow to simplify the present disclosure. These are, of course, merelyexamples and are not intended to be limiting. For example, the formationof a first feature over or on a second feature in the description thatfollows may include embodiments in which the first and second featuresare formed in direct contact, and may also include embodiments in whichadditional features may be formed between the first and second features,such that the first and second features may not be in direct contact. Inaddition, the present disclosure may repeat reference numerals and/orletters in the various examples. This repetition is for the purpose ofsimplicity and clarity and does not in itself dictate a relationshipbetween the various embodiments and/or configurations discussed.

Further, spatially relative terms, such as “beneath,” “below,” “lower,”“above,” “upper” and the like, may be used herein for ease ofdescription to describe one element or feature's relationship to anotherelement(s) or feature(s) as illustrated in the figures. The spatiallyrelative terms are intended to encompass different orientations of thedevice in use or operation in addition to the orientation depicted inthe figures. The apparatus may be otherwise oriented (rotated 90 degreesor at other orientations) and the spatially relative descriptors usedherein may likewise be interpreted accordingly.

During semiconductor fabrication, wafers are moved to differentlocations throughout fabrication machinery. For example, wafers may bemoved (e.g., by robots) between processing chambers and front openingunified pods (FOUPs). Further, the FOUPs may, for example, be used tostore wafers and/or transport wafers between different fabricationmachines. In some instances, a FOUP includes a plurality of slots thatare each configured to securely and safely hold a wafer. When loading orunloading wafers from a FOUP, a robot may be told which slots alreadycontain wafers and which slots do not (i.e., are empty). For example,when removing a wafer from a FOUP, a robot may be told in which slot thewafer is located so that the robot can select the correct wafer.Further, when loading a wafer into a FOUP, a robot may be told whichslots are empty in order to avoid trying to load the wafer into analready occupied slot.

In some instances, if a robot is unaware of which slots contain wafers,the robot may attempt to load a wafer into an already occupied slot,which may cause the wafers to come into contact, which may result indamage to the wafers. Further, in some instances, if the robot isunaware of which slots contain wafers, the robot may attempt to remove awafer from an empty slot, which in turn may waste time and/or resources.

In order to prevent these issues, some fabrication machinery may includewafer mapping sensors that are used to scan the slots of the FOUP todetermine which slots are occupied and which are empty. These wafermapping sensors may, for example, project a point-beam of radiationtoward the slots in the FOUP and measure an intensity of the radiationreflected back toward the sensor. However, these mapping sensors mayhave trouble sensing wafers that have low reflectivity (e.g., glasswafers or some other transparent wafers). For example, because thepoint-beam of radiation comprises a relatively small total amount ofradiation, and because a glass wafer has low reflectivity, the totalamount of radiation reflected by the glass wafer is small. Thus, whenwafers in a FOUP have low reflectivity, these mapping sensors may havelow accuracy when attempting to determine which slots in a FOUP containthe wafers.

Various embodiments of the present disclosure are related to a methodfor detecting wafers in a wafer carrier using an area image sensor toimprove an accuracy of the wafer detection. The method comprises usingthe area image sensor to determine which slots of a wafer carriercontain wafers. For example, the area image sensor generates, with aradiation source, a first beam of radiation toward a first slot of thewafer carrier. The first beam of radiation has a beam area that issubstantially large. In some embodiments, the beam area of the firstbeam of radiation is greater than or equal to a product of a width ofthe first slot multiplied by the distance between slots. The area imagesensor measures, with a radiation sensor, a reflected portion of thefirst beam of radiation that reflected back toward the radiation sensor.Sensor control circuitry then determines if a wafer is in the first slotbased on the measured reflected portion of first beam.

By using the area image sensor to detect wafers in the wafer carrier, anaccuracy of the wafer detection may be improved. For example, becausethe area image sensor generates radiation having a large area, arelatively large total amount of radiation is generated toward the FOUP,and thus even if the reflectivity of the wafers in the FOUP is low, thetotal amount of radiation reflected will be high. For example, theradiation area and the sensing area are larger than or equal to a wafer,so as to cover a whole wafer.

FIG. 1 illustrates a cross-sectional view 100 of some embodiments of aprocess tool comprising an area image sensor 102 for mapping wafers 110in a FOUP 114.

The area image sensor 102 and the FOUP 114 are arranged within asemiconductor fabrication machine housing 116. The FOUP 114 comprises aplurality of slots 122. In some embodiments, each of the slots 122 ofthe FOUP 114 comprise one or more shelves 112. The plurality of slots122 are vertically stacked along a z-axis 101 z. Each slot of theplurality of slots 122 is configured to hold a wafer 110. In otherwords, the one or more shelves 112 of each slot 122 are configured tohold the wafer 110. The slots 122 have openings on one side of the FOUP114 such that the wafers 110 may be moved into and/or out of the slots122 along an x-axis 101 x.

In some embodiments, the area image sensor 102 is arranged on a firstactuator 104. In such embodiments, the first actuator 104 is configuredto move the area image sensor 102 in an upward direction 104 a and in adownward direction 104 b along the z-axis 101 z.

In some embodiments, a focusing device 118 is attached to the area imagesensor 102 by way of one or more second actuators 120. In suchembodiments, the one or more second actuators 120 are configured to movethe focusing device 118 along the x-axis 101 x. In some otherembodiments (not shown), the focusing device 118 is integrated withinthe area image sensor 102. In such other embodiments, the focusingdevice 118 may be moved along the x-axis 101 x within the area imagesensor 102 by one or more internal actuators (not shown).

The area image sensor 102 is configured to generate a beam of radiation108 (e.g., electromagnetic radiation) toward the FOUP 114 and/or towarda wafer 110 in the FOUP 114. The beam of radiation 108 has a beam area(e.g., an area of the FOUP 114 and/or wafer 110 on which the beam ofradiation 108 impinges) that is substantially large. For example, insome embodiments, the beam area is greater than or equal to a product ofa width (e.g., 210 of FIG. 2) of a slot 122 of the FOUP 114 multipliedby the vertical distance (e.g., 212 of FIG. 2) between slots 122 of theFOUP 114. In other words, in some embodiments, the beam area spans oneor more slots of the plurality of slots 122 (e.g., the beam area isgreater than or approximately equal to the area of the opening of oneslot). In some embodiments, the beam area measured at the area imagesensor 102 is greater than the beam area measured at the FOUP 114 (e.g.,the area of the beam increases as the distance from the area imagesensor 102 increases).

In some embodiments, the focusing device 118 is configured to adjust thebeam area of the radiation. For example, by moving the focusing device118 along the x-axis 101 x (e.g., via the one or more second actuators120 or the one or more internal actuators (not shown)), the beam areamay be increased or decreased.

The area image sensor 102 is also configured to measure an intensity ofa reflected portion (not shown) of the beam of radiation 108 that isreflected off of the FOUP 114 and/or off of the wafer 110 in the FOUP114 back toward the area image sensor 102.

Sensor control circuitry 106 is coupled to the area image sensor 102. Insome embodiments, the sensor control circuitry 106 is arranged outsidethe area image sensor 102. In some other embodiments, the sensor controlcircuitry 106 is arranged within the area image sensor 102. The sensorcontrol circuitry 106 is configured to determine which slots of the FOUP114 are filled and which slots are empty. For example, the sensorcontrol circuitry 106 is configured to determine if a wafer 110 is in afirst slot 122 a of the plurality of slots 122 based on a measuredintensity of a reflected portion of the beam of radiation 108 thatreflected off of the first slot 122 a and/or a wafer 110 in the firstslot 122 a back toward the area image sensor 102.

In some embodiments, the sensor control circuitry 106 is furtherconfigured to determine the positions of any wafers 110 in the slots 122of the FOUP 114. For example, if the sensor control circuitry 106determines that a wafer 110 is in the first slot 122 a, the sensorcontrol circuitry 106 is further configured to determine a position ofthe wafer 110 in the first slot 122 a based off the reflected portion ofradiation 108 that reflected off the wafer 110 in the first slot 122 a.

Because the area image sensor 102 generates radiation having asubstantially large area, the total radiation generated toward the FOUP114 will be high, and thus the total reflected radiation will be higheven if the wafers 110 have low reflectivity. For example, even if thewafers 110 in the FOUP 114 have a reflectivity of just 1%, the totalamount of reflected radiation will be high if the total amount ofradiation generated toward the wafers 110 is very high. Thus, comparedto some conventional sensors which only detect a point or a small partof the wafer 110, the area image sensor 102 may improve an accuracy oftransparent wafer detection.

FIG. 2 illustrates a three-dimensional view 200 of some embodiments of aprocess tool comprising an area image sensor 102 for mapping wafers 110in a FOUP 114.

In some embodiments, the area image sensor 102 comprises an area imagesensor housing 202, a radiation source 204 arranged within the areaimage sensor housing 202, and a radiation sensor 206 arranged within thearea image sensor housing 202. In some embodiments, the radiation sensor206 is adjacent to the radiation source 204. In some embodiments, thearea image sensor housing 202 is arranged on the first actuator 104. Insome embodiments, the radiation source 204 is configured to generate(i.e., emit) a beam of radiation 108. In some embodiments (e.g., asillustrated in FIG. 2), a beam area of the beam of radiation 108 mayhave a height along the z-axis 101 z and width along the y-axis 101 y.In some embodiments, the radiation sensor 206 is configured to measure areflected portion of the beam of radiation 108 that impinges on theradiation sensor 206.

In some embodiments, the sensor control circuitry 106 is arranged withinthe area image sensor housing 202 and is coupled to the radiation sensor206. In some other embodiments (see, for example, FIG. 1), the sensorcontrol circuitry 106 is external to the area image sensor 102, isinternal to the semiconductor fabrication machine housing (e.g., 116 ofFIG. 1), and is coupled to the area image sensor 102. In still otherembodiments (see, for example, FIGS. 7-9), the sensor control circuitry106 is external to the area image sensor 102, is external to thesemiconductor fabrication machine housing (e.g., 116 of FIGS. 7-9), andis coupled to the area image sensor 102. In some embodiments, the sensorcontrol circuitry 106 may, for example, have or exhibit some artificialintelligence or the like (e.g., the sensor control circuitry 106 mayemploy some machine learning mechanism or some other suitableintelligent mechanism).

In some embodiments, a transparent layer 208 is arranged on the areaimage sensor housing 202. For example, the transparent layer 208 may beor comprise a glass cover or the like. In such embodiments, theradiation source 204 emits the beam of radiation 108 through thetransparent layer 208, and the radiation sensor 206 measures thereflected radiation that passes through the transparent layer 208 andimpinges on the radiation sensor 206.

In some embodiments, the radiation source 204 may, for example, be orcomprise a light emitting diode, a light bulb, or some other suitableradiation source.

FIG. 3 illustrates a top view 300 of some embodiments of a process toolcomprising an area image sensor 102 arranged on a transfer robot 304within a semiconductor fabrication machine housing 116.

In some embodiments, the transfer robot 304 is configured to move wafers110 between one or more processing chambers 308 and the slots (e.g., 122of FIG. 1) of the FOUPs 114. In some embodiments, the area image sensor102 is arranged on and/or integrated with the transfer robot 304. Insuch embodiments, the transfer robot 304 may be configured to move thearea image sensor 102 vertically along the z-axis 101 z and/orhorizontally along the y-axis 101 y. In some embodiments, the firstactuator (e.g., 104 of FIGS. 2) and the area image sensor housing (e.g.,202 of FIG. 2) are arranged on the transfer robot 304.

In some other embodiments, the area image sensor may be separated fromthe transfer robot 304, as illustrated by item 302. In some embodiments,the first actuator (e.g., 104 of FIG. 2) and the area image sensorhousing (e.g., 202 of FIG. 2) are separated from the transfer robot 304.

In some embodiments, the transfer robot 304 is arranged on a conveyerdevice 306 that is configured to move the transfer robot 304 and thearea image sensor 102 along a y-axis 101 y between the processingchambers 308 and the FOUPs 114. In some embodiments where the imagesensor (e.g., 302) is separate from the transfer robot 304, the conveyerdevice 306 may also be configured to move the area image sensor (e.g.,302) along the y-axis 101 y between the FOUPs. In some other embodimentswhere the image sensor (e.g., 302) is separate from the transfer robot304, a separate conveyer device (not shown) adjacent to the conveyerdevice 306 may be configured to move the area image sensor (e.g., 304)along the y-axis 101 y.

In some embodiments, the wafers 110 may alternatively be some otherworkpiece or the like. In some embodiments, the FOUP 114 mayalternatively be or comprise a wafer cassette, some other wafer carryingapparatus, some other workpiece carrying apparatus, or some otherworkpiece holding apparatus. In some embodiments, the focusing device118 may, for example, be or comprise a focusing lens, some optical lens,some other lens, or some other suitable apparatus. In some embodiments,the radiation (e.g., 108) may be or comprise infrared radiation, visiblelight radiation, ultraviolet radiation, or some other suitableelectromagnetic radiation. In some embodiments, the conveyer device 306may, for example, be or comprise a motorized track or some othersuitable apparatus.

FIGS. 4 and 5 illustrate three-dimensional views 400 and 500 of someembodiments of a method for scanning a first slot 122 a of a FOUP 114 todetermine if a wafer 110 is in the first slot 122 a. Although FIGS. 4and 5 are described in relation to a method, it will be appreciated thatthe structures disclosed in FIGS. 4 and 5 are not limited to such amethod, but instead may stand alone as structures independent of themethod.

As shown in three-dimensional view 400 of FIG. 4, the radiation source204 generates (i.e., emits) a first beam 108 a of radiation toward a oneor more slots (e.g., 122 a, 122 b, 122 c) of the FOUP 114. For example,the radiation source 204 generates the first beam 108 a of radiationtoward a first slot 122 a of the FOUP 114. In some embodiments, an areaof the first beam 108 a (e.g., an area of the FOUP 114 and/or wafer 110on which the first beam 108 a impinges) is substantially large. In someembodiments, an area of the first beam 108 a is greater than or equal tothe area of the opening of the first slot 122 a. In some embodiments,the area of the opening of the first slot 122 a is defined as the areathat spans between inner sidewalls of the FOUP 114 and between shelves112 of the FOUP 114. In other words, in some embodiments, the area ofthe opening of the first slot 122 a is equal to the product of the widthof the first slot 122 a multiplied by the vertical distance between thefirst slot 122 a and the second slot 122 b.

As shown in three-dimensional view 500 of FIG. 5, the radiation sensor206 measures a reflected portion 108 r of the first beam (e.g., 108 a ofFIG. 4) of radiation that reflected is back toward, and impinges on, theradiation sensor 206. For example, since the first slot 122 a is holdinga wafer 110 in the embodiments illustrated in FIGS. 4 and 5, theradiation sensor 206 measures the reflected portion 108 r of the firstbeam that reflected off of the wafer 110 in the first slot 122 a. Insome embodiments, the radiation sensor 206 also measures the reflectedportion 108 r of the first beam that reflected off of a portion of theFOUP 114 that defines the first slot 122 a (e.g., the shelves (e.g., 112of FIGS. 1 and 2) of the FOUP 114 and/or some other part of the FOUP114).

In some other embodiments, when a wafer is not in the slot beingscanned, for example, the radiation sensor 206 measures the reflectedportion 108 r of the first beam that reflected off of a portion of theFOUP 114 that defines the first slot 122 a.

The sensor control circuitry 106 then determines if a slot is filled ornot based on the measurement of reflected radiation taken by theradiation sensor 206. For example, the sensor control circuitry 106determines if the first slot 122 a is filled based on the measuredreflected portion 108 r of the first beam. Further, if the sensorcontrol circuitry 106 determines that the first slot 122 a is filled,the sensor control circuitry 106 may further determine the position ofthe wafer in the first slot 122 a. Determining the position of the waferin the first slot 122 a may allow the sensor control circuitry todetermine if the wafer is seated properly in the first slot 122 a.

FIG. 6 illustrates a flow diagram of some embodiments of a method 600for determining if a wafer is in a slot of a wafer carrier.

At 602, a beam of radiation is generated toward a slot of a wafercarrier, the beam of radiation having a substantially large beam area.FIG. 4 illustrates a three-dimensional view 400 of some embodimentscorresponding to act 602.

At 604, a reflected portion of the beam of radiation is measured. FIG. 5illustrates a three-dimensional view 500 of some embodimentscorresponding to act 604.

At 606, whether the slot of the wafer carrier is holding a wafer isdetermined based on the measured reflected portion of the beam.

FIGS. 7-9 illustrate cross-sectional views 700-900 of some embodimentsof a method for mapping wafers 110 in a FOUP 114. Although FIGS. 7-9 aredescribed in relation to a method, it will be appreciated that thestructures disclosed in FIGS. 7-9 are not limited to such a method, butinstead may stand alone as structures independent of the method.

As shown in cross-sectional view 700 of FIG. 7, the area image sensor102 is positioned at a first height and the area image sensor 102 scansa first slot 122 a of the FOUP 114. The scan comprises generating (e.g.,with a radiation source) a first beam of radiation 108 a toward thefirst slot 122 a (see, for example, FIG. 4). In some embodiments, thearea of the first beam 108 a is greater than or equal to the area of theopening of the first slot 122 a. The scan also comprises measuring(e.g., with a radiation sensor) a reflected portion (not shown) of thefirst beam of radiation 108 a that is reflected back toward, andimpinges on, the radiation sensor (see, for example, FIG. 5). The sensorcontrol circuitry 106 then determines if a wafer (e.g., a first wafer110 a) is in the first slot 122 a based on the first measurement (e.g.,the measured reflected portion of the first beam of radiation 108 a). Insome embodiments, if the sensor control circuitry 106 determines that awafer (e.g., the first wafer 110 a) is in the first slot 122 a, thesensor control circuitry 106 may further determine the position of thewafer based on the first measurement.

In some embodiments, the focusing device 118 may be moved horizontallyalong the x-axis 101 x to adjust the area of the first beam 108 a priorto and/or during the generation of the first beam of radiation 108 a.

As shown in cross-sectional view 800 of FIG. 8, the area image sensor102 is moved (e.g., by the first actuator 104) vertically along thez-axis 101 z to a second height and the area image sensor 102 scans asecond slot 122 b of the FOUP 114. The scan comprises generating asecond beam of radiation 108 b toward the second slot 122 b. In someembodiments, the area of the second beam 108 b is greater than or equalto the area of the opening of the second slot 122 b. The scan alsocomprises measuring a reflected portion (not shown) of the second beamof radiation 108 b that is reflected back toward, and impinges on, theradiation sensor. The sensor control circuitry 106 then determines if awafer (e.g., a second wafer 110 b) is in the second slot 122 b based onthe second measurement (e.g., the measured reflected portion of thesecond beam of radiation 108 b). In some embodiments, if the sensorcontrol circuitry 106 determines that a wafer (e.g., the second wafer110 b) is in the second slot 122 b, the sensor control circuitry 106 mayfurther determine the position of the wafer based on the secondmeasurement.

In some embodiments, the focusing device 118 may be moved horizontallyto adjust the area of the second beam 108 b prior to and/or during thegeneration of the second beam of radiation 108 b.

As shown in cross-sectional view 900 of FIG. 9, the area image sensor102 is moved (e.g., by the first actuator 104) vertically along thez-axis 101 z to a third height and the area image sensor 102 scans athird slot 122 c of the FOUP 114. The scan comprises generating a thirdbeam of radiation 108 c toward the third slot 122 c. In someembodiments, the area of the third beam 108 c is greater than or equalto the area of the opening of the third slot 122 c. The scan alsocomprises measuring a reflected portion (not shown) of the third beam ofradiation 108 c that is reflected back toward, and impinges on, theradiation sensor. The sensor control circuitry 106 then determines if awafer (e.g., a third wafer 110 c) is in the third slot 122 c based onthe third measurement (e.g., the measured reflected portion of the thirdbeam of radiation 108 c). In some embodiments, if the sensor controlcircuitry 106 determines that a wafer (e.g., the third wafer 110 c) isin the third slot 122 c, the sensor control circuitry 106 may furtherdetermine the position of the wafer based on the third measurement.

In some embodiments, the focusing device 118 may be moved horizontallyto adjust the area of the third beam 108 c prior to and/or during thegeneration of the third beam of radiation 108 c.

In some embodiments, the sensor control circuitry 106 then generates awafer map that lists which of the slots (e.g., 122 a, 122 b, 122 c) areholding wafers 110 and which of the slots are empty. The wafer map isgenerated based on the determinations made regarding the state (e.g.,filled or unfilled) of each of the slots. In some embodiments, the wafermap may also include information about the positions of each of thewafers 110 determined to be in the FOUP 114. For example, the wafer mapmay list which wafers 110 are seated properly in the FOUP 114 and/orwhich wafers 110 are seated improperly in the FOUP 114. In someembodiments, if it is determined that one or more wafers 110 are notseated properly in the FOUP 114, the one or more improperly seatedwafers may be reseated by a transfer robot (e.g., 304 of FIG. 3).

Although FIGS. 7-9 illustrate scanning the slots from bottom to top, itwill be appreciated that in some alternative embodiments, the slots maybe scanned from top to bottom or in some other suitable order.

FIG. 10 illustrates a cross-sectional view 1000 of some alternativeembodiments of a method for mapping wafers 110 in a FOUP 114. AlthoughFIG. 10 is described in relation to a method, it will be appreciatedthat the structure disclosed in FIG. 10 is not limited to such a method,but instead may stand alone as a structure independent of the method.

As shown in cross-sectional view 1000 of FIG. 10, the area image sensor102 scans a first slot 122 a, a second slot 122 b, and a third slot 122c of the FOUP 114 simultaneously. The scan comprises generating a firstbeam of radiation 108 a toward the first slot 122 a, the second slot 122b, and the third slot 122 c. In some embodiments, the area of the firstbeam 108 a spans across the first slot 122 a, the second slot 122 b, andthe third slot 122 c. In some embodiments, the area of the first beam108 a is greater than or equal to the combined area of the opening ofthe first slot 122 a, the opening of the second slot 122 b, and theopening of the third slot 122 c. The scan also comprises measuring areflected portion (not shown) of the first beam of radiation 108 a thatis reflected back toward, and impinges on, the radiation sensor (notshown) of the area image sensor 102. The sensor control circuitry 106then determines which of the slots (e.g., 122 a, 122 b, 122 c) areholding wafers based on the first measurement (e.g., the measuredreflected portion of the first beam of radiation 108 a).

In some embodiments, if the sensor control circuitry 106 determines thata wafer (e.g., a first wafer 110 a, a second wafer 110 b, and/or a thirdwafer) is in any of the first slot 122 a, the second slot 122 b, and/orthe third slot 122 c, the sensor control circuitry 106 may furtherdetermine the position(s) of the wafer(s) based on the firstmeasurement.

In some embodiments, the sensor control circuitry then generates a wafermap based on the first measurement.

Although FIGS. 7-10 illustrate the FOUP 114 having three slots, each ofwhich are holding a wafer, it will be appreciated that in some otherembodiments, the FOUP 114 may have some other number of slots and anynumber of those slots may be filled or empty.

FIG. 11A illustrates a flow diagram of some embodiments of a method 1100for mapping wafers in a wafer carrier.

At 1102, a first beam of radiation is generated toward a first slot of awafer carrier, the first beam having a beam area that is substantiallylarge. FIG. 7 illustrates a cross-sectional view 700 of some embodimentscorresponding to act 1102.

At 1104, a reflected portion of the first beam of radiation is measured.FIG. 7 illustrates a cross-sectional view 700 of some embodimentscorresponding to act 1104.

At 1106, a status of first slot of the wafer carrier (e.g., whether thefirst slot is holding a wafer or is empty) is determined based on themeasured reflected portion of the first beam of radiation.

At 1108, acts 1104 through 1106 are repeated for each slot of the wafercarrier. FIGS. 8 and 9 illustrate cross-sectional views 800 and 900,respectively, of some embodiments corresponding to act 1108.

At 1110, a wafer map is generated based on the determined status (e.g.,filled or empty) of each slot of the wafer carrier.

FIG. 11B illustrates a flow diagram of some alternative embodiments of amethod 1150 for mapping wafers in a wafer carrier.

At 1152, a first beam of radiation is generated toward a plurality ofslots of a wafer carrier, the first beam having a beam area that spansacross the plurality of slots. FIG. 10 illustrates a cross-sectionalview 1000 of some embodiments corresponding to act 1152.

At 1154, a reflected portion of the first beam of radiation is measured.FIG. 10 illustrates a cross-sectional view 1000 of some embodimentscorresponding to act 1154.

At 1156, the status of each of the plurality of slots (e.g., determinewhich slots are holding a wafer) is determined based on the measuredreflected portion of the first beam of radiation.

At 1158, a wafer map is generated based on the determined statuses(e.g., filled or empty) of the plurality of slots.

FIGS. 12-19 illustrate views 1200-1900 of some embodiments of a methodfor mapping wafers 110 in a FOUP 114, adjusting the wafers 110 in theFOUP 114, and remapping the FOUP 114. Although FIGS. 12-19 are describedin relation to a method, it will be appreciated that the structuresdisclosed in FIGS. 12-19 are not limited to such a method, but insteadmay stand alone as structures independent of the method.

As shown in cross-sectional view 1200 of FIG. 12, the area image sensor102 is positioned at a first height and the area image sensor 102 scansa first slot 122 a of a FOUP 114. The scan comprises generating (e.g.,with a radiation source) a first beam of radiation 108 a toward thefirst slot 122 a (see, for example, FIG. 4). In some embodiments, thearea of the first beam 108 a is greater than or equal to the area of theopening of the first slot 122 a. The scan also comprises measuring(e.g., with a radiation sensor) a reflected portion (not shown) of thefirst beam of radiation 108 a that is reflected back toward the areaimage sensor 102 (see, for example, FIG. 5). The sensor controlcircuitry 106 then determines if a wafer 110 is in the first slot 122 abased on the first measurement (e.g., the measured reflected portion ofthe first beam of radiation 108 a).

As shown in cross-sectional view 1300 of FIG. 13, the area image sensor102 is moved vertically to a second height and the area image sensor 102scans a second slot 122 b of the FOUP 114. The scan comprises generatinga second beam of radiation 108 b toward the second slot 122 b. In someembodiments, the area of the second beam 108 b is greater than or equalto the area of the opening of the second slot 122 b. The scan alsocomprises measuring a reflected portion (not shown) of the second beamof radiation 108 b that is reflected back toward the area image sensor102. The sensor control circuitry 106 then determines if a wafer 110 isin the second slot 122 b based on the second measurement (e.g., themeasured reflected portion of the second beam of radiation 108 b).

As shown in cross-sectional view 1400 of FIG. 14, the area image sensor102 is moved vertically to a third height and the area image sensor 102scans a third slot 122 c of the FOUP 114. The scan comprises generatinga third beam of radiation 108 c toward the third slot 122 c. In someembodiments, the area of the third beam 108 c is greater than or equalto the area of the opening of the third slot 122 c. The scan alsocomprises measuring a reflected portion (not shown) of the third beam ofradiation 108 c that is reflected back toward the area image sensor 102.The sensor control circuitry 106 then determines if a wafer 110 is inthe third slot 122 c based on the third measurement (e.g., the measuredreflected portion of the third beam of radiation 108 c).

In some embodiments, the sensor control circuitry then generates a firstwafer map that lists which of the slots are holding wafers and which ofthe slots are empty. The first wafer map may also include the positionsof the wafers in the slots. Although FIGS. 12-14 illustrate scanningeach of the slots individually, it will be appreciated that in somealternative embodiments, each of the slots may be scanned simultaneously(e.g., as illustrated in FIG. 10).

As shown in top view 1500 of FIG. 15 and cross-sectional view 1600 ofFIG. 16, one or more wafers 110 are added to (i.e., placed in) one ormore empty slots (e.g., the second slot 122 b). For example, in someembodiments, a transfer robot 304 may move a wafer 110 from a processingchamber 308 to an empty slot in a FOUP 114. The transfer robot 304 mayknow which slots are empty based on the first wafer map.

In some other embodiments (not shown), one or more wafers 110 areremoved (e.g., by the transfer robot 304) from one or more filled slots.In such embodiments, the one or more wafers 110 way then be moved by thetransfer robot 304 to one or more processing chambers 308.

As shown in cross-sectional view 1700 of FIG. 17, the area image sensoris moved to the first height and the area image sensor 102 scans a firstslot 122 a of a FOUP 114. The scan comprises generating a fourth beam ofradiation 108 d toward the first slot 122 a. In some embodiments, thearea of the fourth beam 108 d is greater than or equal to the area ofthe opening of the first slot 122 a. The scan also comprises measuring areflected portion (not shown) of the fourth beam of radiation 108 d thatis reflected back toward the area image sensor 102. The sensor controlcircuitry 106 then determines if a wafer 110 is in the first slot 122 abased on the fourth measurement (e.g., the measured reflected portion ofthe fourth beam of radiation 108 d).

As shown in cross-sectional view 1800 of FIG. 18, the area image sensor102 is moved to the second height and the area image sensor 102 scans asecond slot 122 b of the FOUP 114. The scan comprises generating a fifthbeam of radiation 108 e toward the second slot 122 b. In someembodiments, the area of the fifth beam 108 e is greater than or equalto the area of the opening of the second slot 122 b. The scan alsocomprises measuring a reflected portion (not shown) of the fifth beam ofradiation 108 e that is reflected back toward the area image sensor 102.The sensor control circuitry 106 then determines if a wafer 110 is inthe second slot 122 b based on the fifth measurement (e.g., the measuredreflected portion of the fifth beam of radiation 108 e).

As shown in cross-sectional view 1900 of FIG. 19, the area image sensor102 is moved to the third height and the area image sensor 102 scans athird slot 122 c of the FOUP 114. The scan comprises generating a sixthbeam of radiation 108 f toward the third slot 122 c. In someembodiments, the area of the sixth beam 108 f is greater than or equalto the area of the opening of the third slot 122 c. The scan alsocomprises measuring a reflected portion (not shown) of the sixth beam ofradiation 108 f that is reflected back toward the area image sensor 102.The sensor control circuitry 106 then determines if a wafer 110 is inthe third slot 122 c based on the sixth measurement (e.g., the measuredreflected portion of the sixth beam of radiation 108 f).

In some embodiments, the sensor control circuitry 106 then generates asecond wafer map that lists which of the slots are currently holdingwafers and which of the slots are empty (e.g., to reflect the new statusof the second slot 122 b). In other words, in some embodiments, thesensor control circuitry 106 generates an updated wafer map thatreflects the changes to the slots illustrated in FIGS. 15 and 16.

Although FIGS. 17-19 illustrate scanning each of the slots individually,it will be appreciated that in some alternative embodiments, each of theslots may be scanned simultaneously (e.g., as illustrated in FIG. 10).

Although FIGS. 17-19 illustrate scanning each of the slots in the sameorder as they were scanned in FIGS. 12-14, it will be appreciated thatin some embodiments, the slots may be scanned in a different order thanthat illustrated in FIGS. 12-14.

Although FIGS. 17-19 illustrated rescanning each slot of the FOUP 114after the one or more wafers have been added and/or removed, in someother embodiments, the method may alternatively comprise scanning onlythe one or more slots that were accessed (e.g., to either remove a waferor add a wafer), and updating only the information pertaining to thoseone or more slots in the first map to form the second map in someembodiments. In some cases, by scanning only the accessed slots, timeand/or some other resources may be saved by avoiding the scanning ofslots that experienced no changes.

FIG. 20 illustrates a flow diagram of some embodiments of a method 2000for mapping wafers in a wafer carrier, adjusting the wafers in the wafercarrier, and remapping the wafer carrier While methods 600, 1100, 1150,and 2000 are illustrated and described below as a series of acts orevents, it will be appreciated that the illustrated ordering of suchacts or events are not to be interpreted in a limiting sense. Forexample, some acts may occur in different orders and/or concurrentlywith other acts or events apart from those illustrated and/or describedherein. In addition, not all illustrated acts may be required toimplement one or more aspects or embodiments of the description herein.Further, one or more of the acts depicted herein may be carried out inone or more separate acts and/or phases.

At 2002, a first beam of radiation is generated toward a first slot of awafer carrier, the first beam having a beam area that is substantiallylarge to cover a wafer. FIG. 12 illustrates a cross-sectional view 1200of some embodiments corresponding to act 2002.

At 2004, a reflected portion of the first beam of radiation is measured.FIG. 12 illustrates a cross-sectional view 1200 of some embodimentscorresponding to act 2004.

At 2006, a status of first slot of the wafer carrier (e.g., whether thefirst slot is holding a wafer or is empty) is determined based on themeasured reflected portion of the first beam of radiation.

At 2008, acts 2004 through 2006 are repeated for each slot of the wafercarrier. FIGS. 13 and 14 illustrate cross-sectional views 1300 and 1400,respectively, of some embodiments corresponding to act 2008.

At 2010, a first wafer map is generated based on the determined status(e.g., filled or empty) of each slot of the wafer carrier.

In some embodiments, either act 2012 a or act 2012 b is be performed inthe method 2000. In some other embodiments, both act 2012 a and act 2012b are performed in the method 2000.

At 2012 a, a wafer is added to an empty slot of the wafer carrier. FIGS.15 and 16 illustrate views 1500 and 1600 of some embodimentscorresponding to act 2012 a.

At 2012 b, a wafer is removed from a filled slot of the wafer carrier.

At 2014, acts 2002 through 2006 are repeated for at least the slot(s)which had a wafer added and/or removed. In some embodiments, acts 2002through 2006 are repeated for each of the slots of the wafer carrier.FIGS. 17-19 illustrate cross-sectional views 1700-1900 of someembodiments corresponding to act 2014.

At 2016, a second wafer map is generated based on the determined status(e.g., filled or empty) of each slot of the wafer carrier.

Thus, the present disclosure relates to a method for detecting wafers ina wafer carrier using an area image sensor to improve an accuracy of thewafer detection.

Accordingly, in some embodiments, the present disclosure relates to amethod. The method comprises generating a first beam of radiation towarda first slot of a workpiece carrier. The first beam of radiation has afirst beam area that is greater than or equal to an area of an openingof the first slot. The method further comprises measuring a reflectedportion of the first beam of radiation that is reflected toward, andimpinges on, a radiation sensor. The method further comprisesdetermining if the first slot of the workpiece carrier is holding aworkpiece based on the measured reflected portion of the first beam ofradiation.

In other embodiments, the present disclosure relates to a method. Themethod comprises generating, with a radiation source, a first beam ofradiation toward a first slot of a workpiece carrier. The first beam ofradiation has a first beam area that is greater than or equal to aproduct of a width of the first slot multiplied by a vertical distancebetween neighboring slots of the workpiece carrier. A radiation sensormeasures a reflected portion of the first beam of radiation that isreflected toward, and impinges on, the radiation sensor. sensor controlcircuitry determines if the first slot of the workpiece carrier isholding a workpiece based on the measured reflected portion of the firstbeam of radiation. A first actuator moves the radiation source and theradiation sensor vertically along a vertical axis that extends frombelow the workpiece carrier to above the workpiece carrier. Theradiation source generates a second beam of radiation toward a secondslot of the workpiece carrier. The second beam of radiation has a secondbeam area that is greater than or equal to a product of a width of thesecond slot multiplied by the vertical distance between neighboringslots. The radiation sensor measures a reflected portion of the secondbeam of radiation that is reflected toward, and impinges on, theradiation sensor. The sensor control circuitry determines if the secondslot of the workpiece carrier is holding a workpiece based on themeasured reflected portion of the second beam of radiation. The sensorcontrol circuitry generates a first workpiece carrier map that listswhich slots of the workpiece carrier are holding workpieces.

In yet other embodiments, the present disclosure relates to a processtool. The process tool comprises a radiation source configured togenerate electromagnetic radiation toward one or more slots of aworkpiece carrier. A radiation sensor is adjacent to the radiationsource and is configured to measure a reflected portion of theelectromagnetic radiation that is reflected toward, and impinges on, theradiation sensor. A first actuator is configured to move the radiationsource and the radiation sensor vertically along a vertical axis thatextends from below the workpiece carrier to above the workpiece carrier.Sensor control circuitry is coupled to the radiation sensor and isconfigured to determine if the one or more slots of the workpiececarrier are holding one or more workpieces based on measurements takenby the radiation sensor.

The foregoing outlines features of several embodiments so that thoseskilled in the art may better understand the aspects of the presentdisclosure. Those skilled in the art should appreciate that they mayreadily use the present disclosure as a basis for designing or modifyingother processes and structures for carrying out the same purposes and/orachieving the same advantages of the embodiments introduced herein.Those skilled in the art should also realize that such equivalentconstructions do not depart from the spirit and scope of the presentdisclosure, and that they may make various changes, substitutions, andalterations herein without departing from the spirit and scope of thepresent disclosure.

What is claimed is:
 1. A method, comprising: generating a first beam ofradiation toward a first slot of a workpiece carrier, wherein the firstbeam of radiation has a first beam area that is greater than or equal toan area of an opening of the first slot; measuring a reflected portionof the first beam of radiation that is reflected toward, and impingeson, a radiation sensor; and determining if the first slot of theworkpiece carrier is holding a workpiece based on the measured reflectedportion of the first beam of radiation.
 2. The method of claim 1,wherein if it is determined that the first slot of the workpiece carrieris holding a workpiece, the method further comprises: determining aposition of the workpiece in the first slot based on the measuredreflected portion of the first beam of radiation.
 3. The method of claim1, further comprising: generating a second beam of radiation toward asecond slot of the workpiece carrier, wherein the second beam ofradiation has a second beam area that is greater than or equal to anarea of an opening of the second slot; measuring a reflected portion ofthe second beam of radiation that is reflected toward, and impinges on,the radiation sensor; and determining if the second slot of theworkpiece carrier is holding a workpiece based on the measured reflectedportion of the second beam of radiation.
 4. The method of claim 1,wherein if it is determined that the first slot of the workpiece carrieris not holding a workpiece, the method further comprises: placing aworkpiece in the first slot of the workpiece carrier.
 5. The method ofclaim 4, further comprising: generating a second beam of radiationtoward the first slot of the workpiece carrier, wherein the second beamof radiation has a second beam area that is greater than or equal to thearea of the opening of the first slot; measuring a reflected portion ofthe second beam of radiation that is reflected toward, and impinges on,the radiation sensor; and determining if the first slot of the workpiececarrier is holding a workpiece based on the measured reflected portionof the first beam of radiation.
 6. The method of claim 1, wherein thefirst beam area spans across the first slot and one or more additionalslots of the workpiece carrier, and wherein the method furthercomprises: determining if each slot of the one or more additional slotsis holding a workpiece based on the measured reflected portion of thefirst beam of radiation.
 7. The method of claim 1, further comprising:generating a workpiece map based on a result of determining if the firstslot of the workpiece carrier is holding a workpiece.
 8. A method,comprising: generating, with a radiation source, a first beam ofradiation toward a first slot of a workpiece carrier, wherein the firstbeam of radiation has a first beam area that is greater than or equal toa product of a width of the first slot multiplied by a vertical distancebetween neighboring slots of the workpiece carrier; measuring, with aradiation sensor, a reflected portion of the first beam of radiationthat is reflected toward, and impinges on, the radiation sensor;determining, with sensor control circuitry, if the first slot of theworkpiece carrier is holding a workpiece based on the measured reflectedportion of the first beam of radiation; moving, with a first actuator,the radiation source and the radiation sensor vertically along avertical axis that extends from below the workpiece carrier to above theworkpiece carrier; generating, with the radiation source, a second beamof radiation toward a second slot of the workpiece carrier, wherein thesecond beam of radiation has a second beam area that is greater than orequal to a product of a width of the second slot multiplied by thevertical distance between neighboring slots; measuring, with theradiation sensor, a reflected portion of the second beam of radiationthat is reflected toward, and impinges on, the radiation sensor;determining, with the sensor control circuitry, if the second slot ofthe workpiece carrier is holding a workpiece based on the measuredreflected portion of the second beam of radiation; and generating, withthe sensor control circuitry, a first workpiece carrier map that listswhich slots of the workpiece carrier are holding workpieces.
 9. Themethod of claim 8, wherein the first workpiece carrier map furtherincludes positions of each workpiece determined to be in the workpiececarrier.
 10. The method of claim 8, further comprising: adding, with atransfer robot, a workpiece to an empty slot of the workpiece carrier orremoving, with the transfer robot, a workpiece from a filled slot of theworkpiece carrier.
 11. The method of claim 10, further comprising:generating, with the radiation source, a third beam of radiation towardthe first slot of the workpiece carrier, wherein the third beam ofradiation has a third beam area that is greater than or equal to theproduct of the width of the first slot multiplied by the verticaldistance between neighboring slots; measuring, with the radiationsensor, a reflected portion of the third beam of radiation that isreflected toward, and impinges on, the radiation sensor; determining,with the sensor control circuitry, if the first slot of the workpiececarrier is holding a workpiece based on the reflected portion of thethird beam of radiation; moving, with the first actuator, the radiationsource and the radiation sensor vertically along the vertical axis;generating, with the radiation source, a fourth beam of radiation towardthe second slot of the workpiece carrier, wherein the fourth beam ofradiation has a fourth beam area that is greater than or equal to theproduct of the width of the second slot multiplied by the verticaldistance between neighboring slots; measuring, with the radiationsensor, a reflected portion of the fourth beam of radiation that isreflected toward, and impinges on, the radiation sensor; anddetermining, with sensor control circuitry, if the second slot of theworkpiece carrier is holding a workpiece based on the reflected portionof the fourth beam of radiation.
 12. The method of claim 11, furthercomprising: generating a second workpiece carrier map that lists whichslots of the workpiece carrier are holding workpieces.
 13. The method ofclaim 8, further comprising: determining positions of each workpiecethat is in the workpiece carrier to determine if each workpiece isseated properly in the workpiece carrier.
 14. The method of claim 13,wherein if it is determined that a workpiece is improperly seated, themethod further comprises: reseating the improperly seated workpieceusing a transfer robot.
 15. The method of claim 8, further comprising:moving, with one or more second actuators, a focusing devicehorizontally to adjust the first beam area.
 16. A process tool,comprising: a radiation source configured to generate electromagneticradiation toward one or more slots of a workpiece carrier; a radiationsensor adjacent to the radiation source and configured to measure areflected portion of the electromagnetic radiation that is reflectedtoward, and impinges on, the radiation sensor; a first actuatorconfigured to move the radiation source and the radiation sensorvertically along a vertical axis that extends from below the workpiececarrier to above the workpiece carrier; and sensor control circuitrycoupled to the radiation sensor and configured to determine if the oneor more slots of the workpiece carrier are holding one or moreworkpieces based on measurements taken by the radiation sensor.
 17. Theprocess tool of claim 16, wherein the sensor control circuitry isadjacent to the radiation sensor, and wherein the radiation source, theradiation sensor, and the sensor control circuitry are arranged withinan area image sensor housing that is arranged on the first actuator. 18.The process tool of claim 17, further comprising: a transfer robotconfigured to move workpieces into and out of the one or more slots ofthe workpiece carrier.
 19. The process tool of claim 18, wherein thefirst actuator and the area image sensor housing are arranged on thetransfer robot, and wherein the transfer robot is arranged on a conveyerdevice that is configured to move the transfer robot and the area imagesensor housing horizontally.
 20. The process tool of claim 18, whereinthe first actuator and the area image sensor housing are separated fromthe transfer robot, and wherein a conveyer device is configured to movethe area image sensor housing horizontally.